Subject: Re: [PATCH] t1410: fix breakage on case-insensitive filesystems

From: Johannes Sixt <[email-masked]>
Date: Fri, 14 Nov 2014 20:11:18 +0100

(+cc msysgit)

Am 13.11.2014 um 10:08 schrieb Jeff King:
> On Thu, Nov 13, 2014 at 09:50:24AM +0100, Johannes Sixt wrote:
> 
>>> That looks more like it is failing the actual test (i.e., the creation
>>> of branch "one" when there is cruft in the reflog). My guess is that
>>> calling open() on a directory is giving us EACCES instead of EISDIR. Can
>>> you verify that?

That is indeed the case. It's an ancient bug in our wrapper
mingw_open().

>>> If that is the case, then this isn't a new breakage, I think, but just
>>> code we weren't previously exercising. It would be interesting to know
>>> whether:
>>>
>>>   git config core.logallrefupdates true
>>>   git branch one/two
>>>   git branch -d one/two
>>>   git branch one
>>>
>>> works (even without my patch). If so, then there's probably something
>>> else going on.
>>
>> Don't know what you mean with "my patch" (the one I was responding to
>> touches only t1410).
> 
> The patch you are responding to is a fix-up for 9233887, which tweaked
> the code and added those tests in the first place (I doubt it would work
> for you, though, as it has a problem on case-insensitive filesystems).
> 
>> But the sequence works as expected with a version built
>> in September:
> 
> Hmph. So that would mean my theory is not right. Or maybe I am not
> accounting for something else in my analysis.
> 
> I guess it is odd that the test right before the failing one passes (it
> is basically that same sequence, with reflogs turned on for both
> operations), which implies that we are properly getting EISDIR. The only
> difference in the failing test is that reflogs are turned off for the
> "git branch one" operation. But I cannot see why that would be broken if
> the other one passes.

Not a comment, on this paragraph of yours, but while I was walking
through the code with gdb, I was wondering why the reflog directory is
being touched at all when core.logallrefupdates is off (in
log_ref_setup via log_ref_write). With the patch below I now get the
same unlink warning as on Linux.

--- 8< ---
Subject: [PATCH] Windows: correct detection of EISDIR in mingw_open()

According to the Linux open(2) man page, open() returns EISDIR if a
directory was attempted to be opened for writing. Our emulation in
mingw_open() does not get this right: it checks only for O_CREAT. Fix
it to check for one of the write flags.

This fixes a failure in reflog handling, which opens files with
O_APPEND|O_WRONLY, but without O_CREAT, and expects EISDIR when the
named file happens to be a directory.

Signed-off-by: Johannes Sixt <[email-masked]>
---
 compat/mingw.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compat/mingw.c b/compat/mingw.c
index 2ee3fe3..fc64b73 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -312,7 +312,7 @@ int mingw_open (const char *filename, int oflags, ...)
 		return -1;
 	fd = _wopen(wfilename, oflags, mode);
 
-	if (fd < 0 && (oflags & O_CREAT) && errno == EACCES) {
+	if (fd < 0 && (oflags & (O_WRONLY|O_RDWR)) && errno == EACCES) {
 		DWORD attrs = GetFileAttributesW(wfilename);
 		if (attrs != INVALID_FILE_ATTRIBUTES && (attrs & FILE_ATTRIBUTE_DIRECTORY))
 			errno = EISDIR;
-- 
2.0.0.12.gbcf935e

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